Studies of thermodynamic and transport properties of solutiopns containing simple and complex solvents based on the state-of-art experimental and theoretical techniques undoubtfully contribute to better understanding of solutions and dispersed nanoparticles. Solutions of electrolytes and polyelectrolytes play an important role in science in technology. Ions, both simple and complex, take place in vital processes in all living organisms. Water, by far the most important solvent, plays the key role in these processes - the role which is not completely understood yet. Thousands of papers have been published on the, so called, hydrophobic interaction, yet the scientists still argue on its origin and importance. The thermal and chemical stability of DNA and proteins, their interaction with various ligands or with each other, and studies of molecular similarity are important for pharmaceutical industry and medical sciences as well. In environmental research and bio-separation studies it is important to know the properties of polymeric electrolytes and their interaction with metal ions. Our experimental studies complemented with theoretical modeling were always oriented towards better understanding of these phenomena on the molecular level. For this reason various methods of statistical-mechanics were proposed. We believe that our work is important for further improvement of science and technology, perhaps most notably for biomedical research. Our results were published in the leading chemical journals as: Proc. Natl. Acad. Sci. US, J. Am. Chem. Soc., Annu. Rev. Phys. Chem., J. Phys. Chem. B, J. Chem. Phys., J. Stat. Phys., Langmuir, Biochemistry, Biophys. J, J. Biol. Chem. and J. Mol. Biology. Members of our group had invited talks and lectures at several scientific meetings and at foreign universities. The papers published by the group received considerable attention and the number of quotations is above the average.